This invention relates to stain resistant polymeric compositions for the treatment of natural and synthetic fibers containing polyamide linkages.
Nylon has had a dramatic effect on both industry and society since its discovery by W. H. Carothers more than fifty years ago. It is estimated that 75% of all carpet currently produced in the United States, and 46% of all carpet produced in Europe, is prepared from nylon fiber.
Nylon fiber is relatively inexpensive and offers a combination of desirable qualities such as comfort, warmth, and ease of manufacture into a broad range of colors, patterns and textures. However, nylon, as well as other polyamide fibers and fabrics, is easily stained by certain natural and artificial colorants such as those found in coffee, mustard, wine, and soft drinks.
Recently, fluorochemical coatings have been developed that prevent wetting of the carpet surface, by minimizing chemical contact between the carpet surface and substances that can stain the carpet, making the substance easier to remove. Fluorochemicals also provide a physical barrier to staining material Typical fluorochemicals contain a perfluoroalkyl radical having 3-20 carbons, and are produced by condensation of a fluorinated alcohol or fluorinated primary amine with a suitable anhydride or isocyanate, for example, N-ethyl perfluorooctyl-sulfonamidoethanol and toluene diisocyanate reacted in a 2:1 molar ratio.
Examples of commercially available fluorochemical coatings include Scotchgard.sup..TM. 358 and 352 (Minnesota Mining & Mfg. Co.) and Zepel.sup..TM. and Teflon.sup..TM. (E. I. Du Pont Nemours & Co.). Antron Plus.sup..TM. carpet manufactured by Du Pont contains nylon carpet fibers coated with fluorocarbons.
While fluorochemical coatings are effective in protecting carpet from substances such as soil, they offer little protection from stains resulting from acid dyes that are found in common household materials such as wine, mustard and soft drinks. Acid dyes are bases that bond to protonated amino sites in the polyamide fiber. A wide variety of methods have been developed to make fibers containing polyamide linkages more resistant to staining by acid dyes. The most widely used method involves the application to the polyamide fiber of a colorless formaldehyde phenol or naphthol condensation polymer that has sulfonate groups on the aromatic rings. The sulfonate groups ionically bond to available protonated amino groups in the polyamide fiber, preventing the protonated amino groups from later bonding to common household acid dyes. The polymeric coating also protects the carpet fiber by creating a barrier of negative electric charge at the surface of the fiber that prevents like-charged acid dyes from penetrating the fiber.
Examples of phenol-formaldehyde condensation polymers are described in U.S. Pat. No. 4,501,591 to Ucci, et al., and U.S. Pat. Nos. 4,592,940 and 4,680,212 to Blythe, et al. In particular, U.S. Pat. Nos. 4,592,940 and 4,680,212 describe a formaldehyde condensation product formed from a mixture of sulfonated dihydroxydiphenylsulfone and phenylsulphonic acid, wherein at least 40% of the repeating units contain an --SO.sub.3 X radical, and at least 40% of the repeating units are dihydroxydiphenylsulfone.
Sulfonated hydroxyaromatic formaldehyde condensation products marketed as stain resistant agents include Erional.TM. NW (Ciba-Geigy Limited), Intratex N.TM. (Crompton & Knowles Corp.), Mesitol.TM. NBS (Mobay Corporation), FX-369 (Minnesota Mining & Mfg. Co.), CB-130 (Grifftex Corp.), and Nylofixan P (Sandoz Chemical Corp.) Antron Stainmaster.TM. carpet manufactured by Du Pont contains nylon fibers that have both a fluorocarbon coating and a sulfonated phenol-formaldehyde condensation polymeric coating.
While sulfonated hydroxyaromatic formaldehyde condensation polymeric coatings reduce the staining of polyamide fibers by acid dyes, they do not impart resistance to staining by compounds such as mustard with tumeric or hot coffee. Further, although the polymeric coating is colorless when applied, the resins react with ultraviolet light or nitrogen dioxide over time, gradually turning yellow. The yellowing can be severe enough to prevent the use of the stain resistant compositions on light shaded textile articles.
Efforts to overcome the discoloration problem are discussed in U.S. Pat. No. 4,780,099 to Greschler, et al., describing the reduction of yellowing by application of phenol formaldehyde condensation stain resistant compositions at pH values of 1.5-2.5, and in European Patent Application 87301180.3 by E. I. Du Pont Nemours & Co., describing that polyamide fabrics treated with etherified or acylated formaldehyde phenol condensation polymers containing 10-25% SO.sub.3 groups and 75-90% SO.sub.3 groups that have improved resistance to staining as well as discoloration.
While the performance of stain resistant compositions have been improved, none of the stain resistant compositions currently available offer a suitable combination of protection from staining by common household products such as mustard, coffee, and soft drinks, that also do not discolor over time.
It is therefore an object of the present invention to provide a stain resistant composition that protects polyamide carpets, upholstery, and other synthetic and natural fibers from staining.
It is a further object of the present invention to provide a stain resistant composition that does not yellow significantly over time.
It is still another object of the present invention to provide methods for coating natural and synthetic fibers that are effective, versatile, economical and result in products that are resistant to staining by many common household compounds, including coffee, mustard, wine and soft drinks.
It is a still further object of the present invention to provide natural and synthetic fibers coated with these stain resistant compositions that do not discolor significantly over time.
It is yet another object of the present invention to provide a method for preparing a stain resistant composition.